Ag 첨가가 7050 Al 합금의 기계적 성질에 미치는 영향

권숙인,신명철,곽서희,정영훈,조권구 한국열처리공학회 1999 熱處理工學會誌 Vol.12 No.2

The effects of Ag addition on the microstructures and mechanical properties of 7050 Al alloy were investigated. Various homogenizing and aging treatments were carried out to analyze the controversial effects of Ag in 7050 Al alloy. Transmission electron microscopy(TEM) was used for microstructural analysis. The hardening precipitates(η') become finer with Ag addition. It suggests that Ag promotes easier nucleation of η'. The strength of overaged Ag bearing alloys are higher than that of Ag free alloy. Hardening precipitates(η') in Ag bearing alloys are smaller than that of Ag free alloys, because the growth rate of η' during overaging stage is lower in Ag bearing alloys.

410L 스테인레스 강의 ABS 센서 링 제조를 위한 자기적 특성에 관한 연구

임종국,양현수,곽창섭 한국열처리공학회 1998 熱處理工學會誌 Vol.11 No.4

It is well known for 410L ferritic stainless steel powder to applicate a sensor ring in anti-lock brake system of automobile, several studies, because of its excellent magnetic properties. This study was carried out to investigate the magnetic properties such as the maximum magnetic induction, coercivity and maximum permeability of the materials with functions of sintering density, time and temperature, and concluded as follows: 1. Sintering under the circumstances of Ar gas and the temperature of 1250℃ for 60min. showed that nitrogen was increased, whereas carbon and oxygen decreased in quantities. 2. Both maximum magnetic induction value of 4700Gauss and permeability of 200 were obtained at the maximum sintering density of 6.89g/㎠. Here, the properties showed a linear increasement with increasing the sintering density. 3. Coercivity sharply decreased with incresing the sintering density and reached to 7.6Oe at the maximum sintering density of 6.89g/㎠.

고온 고습하에서 CFRP 적층 원통부재의 충격 압궤특성

김정호,곽훈이,양인영 한국산업안전학회 1998 한국안전학회지 Vol.13 No.2

In this study, in order to measure energy-absorbing characteristics in impact test of CFRP thin-walled laminates and interpret the cause of decreasing age when collapse test is carried out under the environments of high temperatures and hygrothermals, the moisture absorbing behavior according to the variety of orientation angle is observed and impact collapse characteristics of no moisture absorbing status is compared with that under the environments of high temperatures and hygrothermals. Especially, we try to obtain quantitative design data to develop CFRP thin-walled laminates with energy characteristics of optimum impact absorbing. The value of the maximum loading, mean loading, rate of energy absorption energy per unit volume and mass in CFRP thin-walled laminates on the high temperatures and hygrothermals is measured much lower than under no moisture absorbing. The maximum collapse loading in dynamic impact test is taken measurements lower than in static collapse test CFRP circular laminates in high temperatures and hygrothermals. But the absorbed energy per unit mass and volume is almost same each other and the biggest amount of energy is shown in CFRP circular laminates with orientation angle of 15˚. Therefore, in the case of using CFRP circular laminates with axisymmetric mode, CFRP thin-walled structural members with orientation angle of 10˚, 15˚ has generally best condition.

질소/인 동시제거를 위한 하수의 화학적 처리 : 소규모 파일럿실험을 중심으로

곽종운,최정환 한국수처리기술연구회 1994 한국수처리학회지 Vol.2 No.3

The main purpose of this paper is to illustrate how the chemical sewage treatment has been influenced on the removal of nitrogen and phosphorus from the municipal sewage water. A pilot system adjacent to a sewage treatment plant was designed to evaluate the efficacy in removing nitrogen and phosphorus. The chemical treatment step for this system included flocculation and sedimentation. In the test period of about four weeks, the pilot plant for chemical/biological treatment using a coagulant of prepolmerized Hi-PAX was operated in comparison with the conventional biological treatment. The appropriate dosage was 33 ㎕/ℓ to all tested process and the corresponding flow rate of sewage water to be treated was 500 ℓ/day. In our study, phosphorus was possible to remove up to 79% from 4.23 ppm of raw sewage water due to the precipitation with aluminium component from the coagulant used. Chemical precipitation had a positive effect on the denitrification because of a lower carbon to nitrogen ratio. In order to enhance denitrification rate, acetic acid as single carbon source was added to the reaction zone at equivalent rates, showing about 93% in the removal of nitrogen.

화학적 처리에 의한 1 차 하수처리장의 처리효과 개선 : 현장시험을 중심으로

곽종운,김승현,이찬원 대한상하수도학회 1997 상하수도학회지 Vol.11 No.1

Synthesis, crystal structures, and deprotonation of cis- and trans-octahedral nickel(II) complexes with a 14-membered tetraaza macrocycle bearing two N-phenacyl pendant arms

Kim, H.,Kang, S.G.,Kwak, C.H. Elsevier Sequoia [etc.] 2012 Inorganica chimica acta Vol.387 No.-

The di-N-functionalized macrocycle 2,13-bis(2-phenacyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.<SUP>1.18</SUP>0<SUP>7.12</SUP>]docosane (H<SUB>2</SUB>L<SUP>2</SUP>) bearing two N-CH<SUB>2</SUB>COC<SUB>6</SUB>H<SUB>5</SUB> groups has been prepared by the reaction of 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.0<SUP>7.12</SUP>]docosane (L<SUP>1</SUP>) with phenacyl bromide. Interestingly, H<SUB>2</SUB>L<SUP>2</SUP> reacts with Ni<SUP>2+</SUP> ion to form two geometric isomers, trans-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP> and cis-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP>. The axial Ni-O (N-CH<SUB>2</SUB>COC<SUB>6</SUB>H<SUB>5</SUB> group) bond distance (2.080(2)A) of trans-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)](ClO<SUB>4</SUB>)<SUB>2</SUB>.2DMSO is shorter than the in-plane Ni-N distances (2.096(2) and 2.100(2)A). However, the Ni-O distances (2.105(2) and 2.124(2)A) of cis-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)](ClO<SUB>4</SUB>)<SUB>2</SUB>.H<SUB>2</SUB>O are considerably longer than the Ni-N distances (2.053(2)-2.086(2)A). Each N-CH<SUB>2</SUB>COC<SUB>6</SUB>H<SUB>5</SUB> group of trans-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP> and cis-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP> exists as its keto form in the solid state and in various solvents. Two N-CH<SUB>2</SUB>COC<SUB>6</SUB>H<SUB>5</SUB> groups of trans-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP> are readily deprotonated in basic aqueous solutions, producing the enolate form trans-[Ni(L<SUP>2</SUP>)]. On the other hand, cis-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP> undergoes deprotonation to yield cis-[Ni(HL<SUP>2</SUP>)]<SUP>+</SUP>, in which one N-CH<SUB>2</SUB>COC<SUB>6</SUB>H<SUB>5</SUB> group is not deprotonated, under similar conditions.

Fermentation for Liquid-type Yogurt with Lactobacillus casei 911LC

Ko, I.H.,Wang, M.K.,Jeon, B.J.,Kwak, H.S. Asian Australasian Association of Animal Productio 2005 Animal Bioscience Vol.18 No.1

This study was carried out to find the attributes for liquid-type yogurt with Lactobacillus casei 911LC during 72 h fermentation at $37^{\circ}C$. The pH decreased up to 32 h and plauteaued thereafter, and the titratable acidity increased up to 40 h. The growth of lactic acid bacteria sharply increased with $3.5{\times}10^7$ cfu/ml up to 40 h of fermentation and slowly decreased thereafter. The free amino acids produced during fermentation reached the maximum value at 44 h and gradually decreased thereafter. Bitterness sensory scores were the highest at 44 h of fermentation. In the result of electrophoresis, the band mostly disappeared at 72 h fermentation. The present data showed that the range of optimum fermentation time for liquid-type yogurt using Lactobacillus casei 911LC was from 40 to 44 h.

Preparation and characterization of NbF₅-added Mg hydrogen storage alloy

Lee, S.H.,Kwak, Y.J.,Park, H.R.,Song, M.Y. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.29

A sample with a composition of 95 wt% Mg-5 wt% NbF<SUB>5</SUB> (named Mg-5NbF<SUB>5</SUB>) was prepared by reactive mechanical grinding using Mg instead of MgH<SUB>2</SUB> as a starting material. Its hydriding and dehydriding rates were then measured under nearly constant hydrogen pressures. The activation of Mg-5NbF<SUB>5</SUB> was not required, and Mg-5NbF<SUB>5</SUB> had an effective hydrogen storage capacity, which was defined as the quantity of hydrogen absorbed for 60 min, of 5.50 wt%. At the first cycle (n = 1) at 593 K, the sample absorbed 4.37 wt% H for 5 min and 5.50 wt% H for 30 min under 12 bar H<SUB>2</SUB>, and desorbed 1.03 wt% H for 5 min, 4.66 wt% H for 30 min, and 5.43 wt% H for 60 min under 1.0 bar H<SUB>2</SUB>. Reactive mechanical grinding of Mg with NbF<SUB>5</SUB>, which formed MgH<SUB>2</SUB>, MgF<SUB>2</SUB>, NbH<SUB>2</SUB>, and NbF<SUB>3</SUB> by the reaction of 11 Mg + 7NbF<SUB>5</SUB> + 3H<SUB>2</SUB> → MgH<SUB>2</SUB> + 10MgF<SUB>2</SUB> + 2NbH<SUB>2</SUB> + 5NbF<SUB>3</SUB>, is considered to create defects, to produce reactive clean surfaces, and to reduce the particle size of Mg. The XRD pattern of Mg-5NbF<SUB>5</SUB> dehydrided at n = 3 revealed Mg, small amounts of β-MgH<SUB>2</SUB> and MgO, and very small amounts of MgF<SUB>2</SUB> and NbH<SUB>2</SUB>. An increase in the dehydriding rate of Mg-5NbF<SUB>5</SUB> was attempted by adding Ni to Mg-5NbF<SUB>5</SUB>. Mg-5NbF<SUB>5</SUB> had higher initial hydriding and dehydriding (after the incubation period) rates and a larger effective hydrogen storage capacity than Mg-10NbF<SUB>5</SUB>, Mg-10MnO, and Mg-10Fe<SUB>2</SUB>O<SUB>3</SUB>, which were reported to have quite high hydriding rate and/or dehydriding rate.

Development of a Mg-based hydrogen-storage material by addition of Ni and NbF₅ via milling under hydrogen

Kwak, Y.J.,Lee, S.H.,Mumm, D.R.,Song, M.Y. Pergamon Press ; Elsevier Science Ltd 2015 International journal of hydrogen energy Vol.40 No.35

Milling under hydrogen was used to prepare samples with a composition of 80 wt% Mg + 14 wt% Ni + 6 wt% NbF<SUB>5</SUB> (named 80Mg + 14Ni + 6NbF<SUB>5</SUB>). 80Mg + 14Ni + 6NbF<SUB>5</SUB> had a large effective storage capacity of hydrogen of approximately 5.6 wt% H. The activation of 80Mg + 14Ni + 6NbF<SUB>5</SUB> was done after one storing-releasing cycle. At n = 2 at 593 K, 80Mg + 14Ni + 6NbF<SUB>5</SUB> stored 3.92 and 5.57 wt% H after 2.5 and 60 min, respectively, under 12 bar H<SUB>2</SUB>, and released 2.34 and 4.81 wt% H after 10 and 60 min, respectively, under 1.0 bar H<SUB>2</SUB>. The following reaction happened during milling under hydrogen and at the early storing-releasing cycles: 14Mg + Ni + 4NbF<SUB>5</SUB> + 7H<SUB>2</SUB> → MgH<SUB>2</SUB> + Mg<SUB>2</SUB>NiH<SUB>4</SUB> + Mg + 10MgF<SUB>2</SUB> + 4NbH<SUB>2</SUB>. At a fairly low temperature of 423 K, the sample stored 0.28, 0.34, and 0.57 wt% H after 5, 10, and 60 min, respectively. The initial storing rate of 80Mg + 14Ni + 6NbF<SUB>5</SUB> increased as the temperature rose from the room temperature to 573 K since the effect of thermal activation is predominant, and fell as the temperature rose from 573 K to 623 K since the effect of decrease in the driving force for storing reaction is predominant.

Stepwise production of syngas and hydrogen through methane reforming and water splitting by using a cerium oxide redox system

Jeong, H.H.,Kwak, J.H.,Han, G.Y.,Yoon, K.J. Pergamon Press ; Elsevier Science Ltd 2011 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.36 No.23

Stepwise production of syngas and hydrogen from ZrO<SUB>2</SUB>-supported CeO<SUB>2</SUB> through methane reforming and water splitting was investigated in order to find proper operating conditions under which carbon deposition could be minimized. Recommendable operating temperature and time were 1073 K and 30 min for both the methane reforming and the water splitting. Even though the H<SUB>2</SUB>/CO ratio during the methane reforming was maintained close to the desired ratio of 2, undesirable methane cracking occurred to a small extent and further reduction of Ce<SUB>2</SUB>O<SUB>3</SUB> to metallic Ce by CH<SUB>4</SUB> and H<SUB>2</SUB> occurred to some extent. When the methane reforming-water splitting cyclic operations were repeated, the yields of syngas and hydrogen decreased considerably from the first cycle to the second cycle, but from the second cycle to the fifth cycle the gas yields were maintained nearly constant. As the CeO<SUB>2</SUB> content in the sample increased, the gas yields per mole of CeO<SUB>2</SUB> decreased but the gas productions per gram of sample increased.